System for reacting alkylaromatics with alkadienes

ABSTRACT

A reaction system is disclosed for reacting an alkylaromatic with a conjugated alkadiene, employing a dispersed catalyst such as alkali metal, to produce mainly mono-adduct product. The system includes a stirred reactor, or a plurality of stirred reactors in series, through which the liquid alkylaromatic containing dispersed catalyst is passed. Each reactor has an alkadiene supply line adjustably extending therein with its outlet positioned within the liquid during normal operation and movable to above the liquid prior to shut-down. Means are further provided for supplying an inert gas to each supply line in place of alkadiene prior to shut-down. By this arrangement plugging due to polymerization of alkadiene within the supply line can be avoided.

United States Patent 11 1 Mitchell [4 1 Oct. 15,1974

[ SYSTEM FOR REACTING ALKYLAROMATICS WITH ALKADIENES Primary Examiner-Joseph Scovronek Assistant Examiner-Michael S. Marcus [75] Inventor. Richard E. Mltchell, Boothwyn, Pa. Attorney Agent, or g L. Church; Donald [73] Assignee: Sun Research and Development Co., R. Johnson; J. Edward Hess Marcus Hook, Pa. [22] Filed: Sept. 7, 1972 [57] ABSTRACT PP 287,138 A reaction system is disclosed for reacting an alkylaromatic with a conjugated alkadiene, employing a dis- [52] CL 23/288 E, 23/252 R 23/285 persed catalyst such as alkali metal, to produce mainly 51 Int. Cl v. B01j 9/08 Bbl-j 4/00 Pmduct- The System includes a Stirred [58] Field of Search 23/288 A, 288 283 284, reactor, or a plurality of stirred reactors in series,

231/285, 252 R 288 260/668 through which the liquid alkylaromatic containing dispersed catalyst is passed. Each reactor has an alkadi- 5 References Cited ene supply line adjustably extending therein with its outlet positioned within the liquid during normal oper- UNITED STATES PATENTS ation and movable to above the liquid prior to shut- ;325379 2/1946 Sparks et a]. 23/285 down Means are further Provided f Supplying an g inert gas to each supply line in place of alkadiene 2:762:682 9/1956 Van DQv'G;;;;;;.... .111... 23/285 to By Plugging due 2,845,936 8/1958 Boynton et a1. 23/285 Polymenzam of alkadlene the supply 2,903,344 9/1959 Rollman et al 23/288 E can be avoided- 3,3l3,839 4/1967 Rozzi 23/252 R 3,492,283 1 1970 Miller 23/253 A 1 Clam, 2 D'awmg F'gures 2O INERT STIRRED GAS REACTOR l0 REACTION MIXTURE l EFFLUENT l6u\ l2 l3 ALKYLAROMATIC L( p CATALYST H DISPERSION l6 INERT GAS ALKADIENE PATENTEIJIIIIISIIIII I '3.8'41.844

sum-ear 2 I FIG. 2

INERT GAS L INERT GAS DISPERSION OF REACTION ALKYLAROMATIC I MIXTURE- AND CATALYST EFFLUENT SYSTEM FOR REACTING ALKYLAROMATICS WITH ALKADIENES CROSS REFERENCE TO RELATED APPLICATION My copending application Ser. No. 282,995, filed Aug. 23, 1972, now abandoned, relates to a process for reacting alkylbenzen'es with conjugated alkadienes utilizing alkali metal as promoter, for which process the reaction system of the present invention is particularly useful.

BACKGROUND OF THE INVENTION This invention relates to a system for reacting a liquid alkylaromatic hydrocarbon with a conjugated alkadiene in the presence of a dispersed catalyst to yield mainly mono-adduct product, i.e., the one-toone addition product of the alkylaromatic and diene.

The use of alkali metals for catalyzing or promoting the addition of conjugated alkadienes, such as butadiene or isoprene, to alkylaromatic hydrocarbons is known in the prior art and has been disclosed, for example, in the following US. Pat. Nos. 1,934,123, issued Nov. 7, 1933, F. Hofmann et al.,; and 2,603,655, issued July 15, 1952, D. E. Strain. Conditions more favorable for securing good yields ofthe mono-adduct product in such alkenylation reactions have been described by G. G. Eberhardt et al., in J. ORG. CHEM., 30, 82-84 (1965) and in Eberhardt U.S. Pat. No. 3,244,758, issued Apr. 5, 1966. The conditions described in the latter references include utilizing a granular support on which the alkali metal is distended and slowly adding the conjugated diene to the alkylaromatic reactant while vigorously agitating the mixture.

These alkenylation reactions ordinarily would be carried out by maintaining a body of liquid alkylaromatic hydrocarbon containing dispersed catalyst or promoter at a suitable temperature, e.g. 90-140C., and passing a stream of the alkadiene through a feed line extending into the liquid body. Difficulties have been experienced in this kind of operation, however, in cases where it has become necessary, to interrupt the flow of diene through its feed line, as during a temporary shut-down.

It has been found that when the flow of diene is restarted to the system, plugging of the feed line generally occurs and continued operation usually cannot be maintained. The present invention provides a reaction system by which this plugging problem can be avoided.

SUMMARY OF THE INVENTION The reaction system according to the invention includes either a single stirred reactor, or a plurality of stirred reactors in series, through which the liquid alkylaromatic containing dispersed alkali metal catalyst or promoter is passed. The single reactor, or each reactor when a series of reactors is employed, has an alkadiene supply line adjustably extending therein with its outlet positioned within the liquid during normal operation and movable to above the liquid prior to shutdown of the operation. Means are further provided for supplying an inert gas to each supply line in place of alkadiene prior to shut-down. Whenever it becomes'desirable to stop the flow of alkadiene to a reactor, this arrangement allows inert gas to be passed through the supply line therein before the alkadiene flow is stopped, thereby preventing entrance into the line of liquid containing dispersed alkali metal. It also permits the supply line to be raised above the liquid level before How of inert gas therethrough is stopped. By this arrangement the alkali metal promoter can be prevented at all times from entering the alkadiene supply line and adhering to its walls. It has been found that this'will eliminate the plugging problem when alkadiene again is fed to the reactor;

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF EMBODIMENTS The present reaction system can be used for reacting an alkylaromatic hydrocarbon containing benzylic hydrogen with a conjugated diene to produce mainly mono -adduct product. Examples'of such reactants are given in Eberhardt US. Pat. No. 3,244,758 cited above. One example is the alkenylation of o-xylene by means of l,3-butadiene to produce mainly 5-0- tolylpentene-Z. The promoter or catalyst for the reaction can be an alkali metal, such as sodium, potassium or mixtures thereof, dispersed in the alkylaromatic hydrocarbon. The catalyst can, if desired, be used in combination with a-granular support as disclosed in the aforesaid Eberhardt patent.

FIG. lillustrates the invention as applied to a single reactor 10 provided with a stirrer 11 for effectively agitating the reaction mixture therein. A dispersion of the catalyst in the liquid alkylaromatic feed, which has been preformed in any suitable apparatus (not shown), is fed continuously through line 12 and valve 13 into reactor 10. Reaction mixture continuously overflows from an upper part of the reactor, asillustrated by line 14, so that a body of liquid reaction mixture is maintained in the reactor up to the level of line 14. Alkadiene passes to the reactor through control valve 15 and line 16 which has a sparger 17 at its outlet. The alkadiene reactant, which can be fed either as a gas or a liquid into the liquid reaction mixture, becomes immediately dispersed therein due to the action of stirrer 11. Line 16 is movable vertically and normally during operation is positioned with sparger 17 in the lower part of the reactor. However, line 16 can be adjustably extended upwardly so that the sparger will be in the vapor space above the liquid. This position is indicated by dashed line 16a terminating at sparger position 17a. An inert gas line l8provided with control valve 19 connects with supply line 16, and a vent line 20 is located at the top of the reactor for removing inert gas so introduced. Any suitable inert gas, such asnitrogen, helium, argon or the like, can be utilized for this purpose.

The system shown in FIG. I normally operates with the two reactants being continuously fed respectively through valves 12 and 15 and their corresponding lines, with inert gas valve 19 closed and with line 16 extending only into the lower part of reactor 10. In case it becomes desirable to stop the flow of alkadiene for any reason, control valve 19 first is opened to admit inert gas through supply line 16 and sparger 17; The alkadiene flow is then stopped by closing valve 15, following which the supply line and sparger are moved upwardly to the position indicated by 16a and 17a. The inert gas flow then can be stopped, if desired, by closing valve 19. When the normal operation is to be restarted, the inert gas flow is first started again by opening valve 19, the supply line and sparger are moved to the lower position, and the flows of reactants to reactor with stirrer 11 operating are then started by opening control valves 12 and 15, following which the flow of inert gas is stopped by closing valve 19.

This procedure prevents liquid reaction mixture from entering supply line 16 through sparger 17 at all times and thus prevents any of the dispersed catalyst from getting on the inner surfaces of supply line 16 and sparger 17. it has been found that this will eliminate the problem of alkadiene supply line plugging upon resumption of the normal operation.

P16. 2 illustrates a preferred reaction system according to the invention involving a series'of independently stirred reaction zones contained in horizontal tank 30. The preferred number of reactors for such system is 3 to 6, and'FIG. 2 shows a system containing 5 reactors designated as A, B, C, D and E. The reaction zones are separated by baffles 31, 32, 33 and 34 each of which is spaced from the top of tank 30 to permit overflow of the reaction mixture to the next zone. The zones are provided with motorized stirrers35, 36, 37, 38 and 39 for independently stirring the reaction mixture within each zone. A dispersion of the alkylaromatic and catalyst normallyis fed continuously to tank. 30 through line 40, and reaction mixtures passes continuously from the opposite end of the tank through overflow line 41 positioned so as to normally maintain a vapor space in the upper part of the tank.

The alkadiene reactant enters the system through line 42 containing control valve 43 and connected with manifold 44. Leading from the manifold are five supply lines 45, 46, 47, 48 and 49, each of which contains a flow control valve and has a flexible section therebeneath. Each supply line slidably extends down through a packing gland in the top of tank 30 into one of the reaction zones and terminates at a sparger, indicated by numerals 50, 51, 52, 53 and 54, located during normal operation beneath the corresponding stirrer. Manifold 44 is also connected to an inert gas supply line containing flow control valve 55. A vent line 56 is provided at the top of tank 30 for removing inert gas admitted to the system.

The system illustrated in FIG. 2, involving a plurality of reaction zones (preferably 3-6) through which the alkylaromatic component flows in series but to which individual streams of the alkadiene reactant are fed to the respective reactors, permits higher yields of the de- Ser. No. 282,995. During normal operation the alkadiene reactant is fed from manifold 44 through the five supply lines at approximately equal rates to each reaction zone and no inert gas is admitted to the system. At this time the supply lines extend to the lower part of the reaction zones as shown in FIG. 2. Whenever it becomes necessary to stop the alkadiene flow for any reason, inert gas is first admitted through valve 55 to manifold 44 and thence to the five supplylines 45-49. These lines are then moved to an upper position at which each of spargers 50-54 is above the liquid level maintained by overflow line 41. The alkadiene flow can be stopped at any time after the inert gas flows have started through the supply lines, and generally the introduction of alkylaromatic feed through line 40 is stopped at the same time. Once the spargers have been raised to the upper position, the inert gas flow also can be stopped if desired. When it is desired to resume normal operation, the flows of inert gas through lines 45-49 again are started, the lines are moved downwardly to the lower position, feeding of the alkylaromatic and alkadiene reactants is then resumed through lines 40 and 43 respectively, and finally the-flow of inert gas is stopped by closing valve 55. This procedure keeps the catalyst at all times from getting into supply lines 45-49 and thereby precludes any polymerization of alkadiene therein that otherwise could cause these lines to plug.

While a single tank is used to provide the series of reaction zones illustrated in FIG. 2, it is apparent that separate reactor tanks connected at an upper level by flow passages and otherwise provided with the various features described above would be equivalent.

The invention claimed is:

l. A system for reacting liquid alkylaromatic hydrocarbon with a conjugated alkadiene in the presence of dispersed catalyst to produce mainly mono-adduct product, which comprises:

a. reactor means provided with means for stirring a liquid reaction mixture therein;

b. means for introducing alkylaromatic hydrocarbon containing dispersed catalyst to said reactor means;

c. a supply line for introducing conjugated alkadiene to the reactor, said supply line extending into the reactor means with its outlet end adjustably movable from a position within the liquid reaction mixture therein to a position above the liquid mixture;

(1. an outlet line for removing reaction mixture from the reactor means;

e. means for supplying an inert gas in place of conjugated alkadiene to said supply line;

f. and vent means for removing inert gas from the reflCtOI' means. 

1. A SYSTEM FOR REACTING LIQUID ALKYLAROMATIC HYDROCARBON WITH A CONJUGATED ALKADIENE IN THE PRESENCE OF DISPERSED CATALYST TO PRODUCE MAINLY MON-ADDUCT PRODUCT, WHICH COMPRISES: A. REACTOR MEANS PROVIDED WITH MEANS FOR STIRRING A LIQUIDF REACTION MIXTURE THEREIN; B. MEANS FOR INTRODUCING ALKYLAROMATIC HYDROCARBON CONTAINING DISPERSED CATALYST TO SAID REACTOR MEANS; C. A SUPPLY LINE FOR INTRODUCING CONJUGATED ALKADIENE TO THE REACTOR, SAID SUPPLY LINE EXTENDING INTO THE REACTOR MEANS 